For many patients with severe to profound hearing impairment, there are several types of middle-ear and inner-ear implants that can restore a sense of partial or full hearing. For example, cochlear implants can restore some sense of hearing by direct electrical stimulation of the neural tissue of the inner ear or cochlea. The cochlear implant typically includes an electrode carrier having an electrode lead and an electrode array, which is threaded into the cochlea. The electrode array usually includes multiple electrodes on its surface that electrically stimulate auditory nerve tissue with small currents delivered by the electrodes distributed along the electrode array. These electrodes are typically located toward the end of the electrode carrier and are in electrical communication with an electronics module that produces an electrical stimulation signal for the implanted electrodes to stimulate the cochlea.
One of the important steps in cochlear implant surgery is the insertion of the electrode array into the scala tympani of the cochlea. In some cases, this insertion process can be disrupted when the continuous movement of the electrode carrier into the cochlea gets disturbed due to increased frictional forces between the cochlea wall and the electrode array, or due to small obstacles preventing the electrode carrier from smoothly moving along the insertion path. In both cases, the electrode carrier may become damaged if it is excessively bent when being pushed further inside the cochlea while the tip or other parts of the electrode carrier are prevented from moving forward. Furthermore, x-ray microscopy studies by Hüttenbrink et al. allowed a visualization of the frictional behaviour of electrodes in the inner ear and revealed that in some cases there might be the danger of kinking of the electrode carrier inside of the scala tympani. A subsequent contact pressure between electrode and basilar membrane which may lead to rupture of the basilar membrane is very likely to damage anatomical structures of the inner ear and destroy residual hearing. Such damage is not acceptable with the latest trends in Electric Acoustic Stimulation (EAS) technology and cochlear implant surgery to preserve any residual hearing.
To minimize these problems, lubricating substances are sometimes used on the electrode carrier to reduce the frictional forces between electrode carrier and the cochlea. However, it is questionable whether these lubricating substances are able to prevent typically occurring problems during the insertion process and currently have not become a commonly accepted clinical practice.
Another issue which is observed in cochlear implant surgery is the floppiness of the electrode carrier in the mastoidectomy and posterior tympanatomy which may make it difficult to guide the electrode carrier to the cochleostomy or round window without picking up blood or other fluids from the surrounding tissues. A contamination of the electrode carrier with blood represents another potential hazard to the residual hearing of patients.
U.S. Patent Application Publication No. 2007/0225787 to Simaan et. al. (“Simaan”) teaches active-bending electrodes and corresponding insertion systems for inserting same. In this context, an electrode applicator is mentioned which reduces the frictional forces as the electrode traverses the inner ear by applying vibrations to the electrode array. However, the insertion systems disclosed therein include a controller located remotely, making the systems bigger and more unwieldy. In addition, Simaan fails to provide any teachings on how, and by what mechanism, the insertion system generates the vibrations in the electrode array.